He’s talking about in-world legal bans on races. In other threads he has used examples of how in Matt Colville’s lore, Dragonborn are banned by the evil Lord Ajax the Invincible since they are a symbol of the previous regime, and he has enforced that via a hefty bounty.

I ran a short campaign where Warforged were heavily legally restricted. If you played one, you did not legally count as a person, and could not conduct activities without your owner. If you were by yourself, you needed to be unarmed and unclothed except for an amulet from the noble house of your owner. The plot ended up being basically Django Unchained.